Putting functions in a header file

Ok I am learning how to put functions that i write into a header file and then including that file in my source code. But I keep getting and error for undefined reference to rndNumber(), but the other function I have works fine when I call it. Here is the code to my header file:

About the undefined references:
if you're using an IDE and add your myfunctions.c and main.c to the default project, it should compile well.
If you're using a command line compiler, 1st you have to compile each of the *c. files separately and then link them all together.
Using gcc here's an examle:
1# gcc myfunctions.c -c
2# gcc main.c -c
3# gcc myfunctions.o main.o -o myprog.exe
or
4#gcc myfunctions.c main.c -o myprog.exe
On 1# and 2# you source files are compiled, and on 3# they're linked together to create a final executable.
That undefined reference happens because in your main.c you include myfunctions.h which declare a function that you use. That's only a declaration, something to mention the compiler that those symbols are funtions that receive x arguments and return something. Then when you link the final file the compiler MUST know here the compiled function is, the binaries.
4# is just a short hand for 1#,2# and 3#.
If you're working with a large project, separating your source through several files is a way to organize you code, and to reduce compilation time, because you only need to compile the file that you change, and re-link.

Its good that everyone was so helpful. goto statements are to C programmers as garlic is to vampires. Also, kbhit() is not a portable function. Those are only me and other being picky about what you are doing, your way works and you don't have to change it if you don't want to.